Auto-relieving pressure modulating valve

ABSTRACT

An auto-relieving pressure modulating valve includes a spool, a solenoid that shifts the spool in an energized direction, and a spring arrangement. The spring arrangement functions to shift the spool from a relieving position to a neutral position, in the energized direction, without energizing the solenoid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 09/976,383,filed Oct. 11, 2001, now U.S. Pat. No. 6,609,538; which application isincorporated herein by reference.

FIELD OF THE INVENTION

This disclosure concerns a solenoid valve assembly. More specifically,this disclosure describes a solenoid actuated brake or actuatorassembly.

BACKGROUND OF THE INVENTION

A wide variety of electrohydraulic pressure reducing and relievingvalves are used to provide controlled pressure to hydraulic actuatorsand brake cylinders, for example. Some typical valves are designed foruse with a proportional electric solenoid, which generates a thrustforce proportional to the electrical current fed to the solenoid. Thesize and cost of the proportional solenoid are a function of the forceoutput and the stroke over which this force output is available. Thrustforce of proportional solenoid valves is proportional only within apredetermined stroke length. For a given size and cost, thepredetermined proportional stroke length may be exceeded, but only withreduced force. Thus, to maximize the force capability of a proportionalsolenoid valve, it is desirable to maintain the stroke length within theproportional range. Typical proportional solenoid valves have movingarmatures that travel farther than the proportional stroke range.Farther travel in the valve is desirable to provide for quickeractivation or release of a working unit by increasing the flow ratethrough the valve body. Moving the armature as far over as possible inan activation or release position increases the flow rate. The problemis that as the stroke of the armature exceeds the proportional range,the thrust force rapidly decreases. Therefore, current designs arelimited in providing adequate flow rate due to the constraint of therelationship between stroke length and force output.

In general, improvement has been sought with respect to such valvearrangements, generally to better accommodate increasing overall valvespool and armature travel while maintaining proportional stroke lengthto maximize force output.

SUMMARY OF THE INVENTION

One aspect of the present invention relates to a solenoid valve assemblyhaving an auto-relieving valve arrangement that utilizes the maximumstroke length and force output of a proportional solenoid valve whileproviding added stroke travel to increase flow rate capacity withoutexceeding the solenoid's proportional range.

Another aspect of the present invention relates to a valve arrangementhaving a biasing component that biases a spool in an energizeddirection, from a relieving position to a neutral position, withoutenergizing a solenoid.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of principles of thisdisclosure and, together with the description, serve to explain theseprinciples.

FIG. 1 is a cross-sectional view of one embodiment an auto-relievingvalve arrangement shown in a neutral position according to theprinciples of this disclosure.

FIG. 2 is a cross-sectional view of the auto-relieving valve arrangementof FIG. 1, shown in an energized position.

FIG. 3 is a cross-sectional view of the auto-relieving valve arrangementof FIG. 1, shown in a relieving position.

FIG. 4 is a cross-sectional view of a spool taken along line 4—4 shownin FIG. 1.

FIG. 5 is a cross-sectional view of the spool taken along line 5—5 shownin FIG. 1.

FIG. 6 is a cross-sectional view of another embodiment of anauto-relieving valve arrangement shown in a neutral position accordingto the principles of this disclosure.

FIG. 7 is a cross-sectional view of the auto-relieving valve arrangementof FIG. 6, shown in an energized position.

FIG. 8 is a cross-sectional view of the auto-relieving valve arrangementof FIG. 6, shown in relieving position.

FIG. 9 is a side view of the washer shown in FIG. 6.

FIG. 10 is a front view of the washer of FIG. 9.

DETAILED DESCRIPTION

With reference now to the various drawing figures in which identicalelements are numbered identically throughout, a description of variousexemplary aspects of the present invention will now be provided.

FIG. 1 illustrates, in cross-section, one embodiment of a valve assembly10 according to the principles of this disclosure. In general, the valveassembly 10 includes a valve body 26 coupled to a solenoid assembly 28.Typically, the valve assembly 10 is used in conjunction with a hydraulicpressure unit or hydraulic pump 12, a hydraulic reservoir or tank 14,and a working unit 16 such as, for example, a hydraulic cylinder orbrake.

For purposes of clarification, the valve assembly 10 will be describedas having a first end 36 and a second end 38. Also, the valve assembly10 will be described as having components moving in an energizeddirection 36′ and a de-energized direction 38′. The energized direction36′ is opposite the de-energized direction 38′.

The valve body 26 of the valve assembly 10 includes a bore 24, apressure port 18, a work port 20, and a tank port 22. The bore 24typically extends through the valve body 26. Each of the ports 18, 20and 22 are in fluid communication with the bore 24. In the illustratedembodiment, the pressure port 18 is disposed proximate the first end 36and the tank port is disposed proximate the second end 38. The work port20 is disposed intermediate the pressure and tank ports 18, 22. As shownschematically in FIG. 1, the ports 18, 20, and 22 provide connectionlocations for establishing fluid communication between the valve body 26and the hydraulic pump 12, the working unit 16, and the tank 14. Typicalport connections include standard SAE straight threads or otherconfigurations for allowing hoses or other conduits to be connectedbetween the components.

Alternative embodiments having other port configurations arecontemplated, for example, the pressure port 18 may be disposedproximate the second end 38 and the tank port 22 may be disposedproximate the first end 36. A second embodiment, which discloses anotheralternative configuration, is described in detail below.

The bore 24 includes a first annular surface 30 and a second annularsurface 32. These surfaces cooperate with the solenoid assembly todirect fluid communication between the ports 18, 20, and 22 as thesolenoid assembly is energized and de-energized. The bore 24 alsoincludes a countersink region 34. In the illustrated embodiment, thecounter sink region 34 is proximate the second end 38.

The bore 24 is configured to receive a spool 42 of the solenoid assembly28. The solenoid assembly 28 generally includes an armature (not shown),such as a common coil and iron core armature. The spool 42 is coupled tothe armature so that when the solenoid assembly 28 is energized, thespool 42 moves in accordance with the armature from a de-energizedneutral position to an energized position. The neutral position and theenergized position of the spool 42 are shown in FIGS. 1 and 2respectively. In the illustrated neutral position of FIG. 1, fluidcommunication is provided between the work port 20 and the tank port 22.The energized position (shown in FIG. 2), provides fluid communication(as shown by the arrow) between the pressure port 18 and the work port20. It is to be understood that the solenoid may operate in thealternative where, for example, the energized position provides fluidcommunication between a work port and a tank port and the neutralposition provides fluid communication between a pressure port and thework port.

The spool 42 includes a first annular portion 44 and a second annularportion 46. The annular portions 44 and 46 are configured to coincidewith the first and second annular surfaces 30 and 32 of the bore 24. Thespool 42 also comprises a shoulder 48 proximate the second end 38 of thevalve assembly 10.

In the illustrated embodiment, the valve assembly 10 includes a spring50 and a spring retaining member 54. The retaining member 54 may be anextended portion of the solenoid assembly 28 or a separate valveassembly component. The spring 50 is positioned within the countersinkregion 34 of the bore 24. The spring 50 may comprise a variety ofcompression spring configurations. Other spring types that may be usedinclude bevel springs, torsion springs with levers, leaf springs, andthe like.

The spring retaining member 54 is configured with an interior shoulder56. The spring 50 is positioned longitudinally between the shoulder 48of the spool 42 and the interior shoulder 56 of the retaining member 54.The retaining member 54 functions as a stationary component againstwhich the spring 50 is compressed. In the illustrated embodiment, thespool 42 includes an extended portion 58 having an inside diameter sizedto guide the spring 50. The extended portion 58 maintains the spring 50in a longitudinal orientation.

In the illustrated embodiment, a washer 60 is disposed between theshoulder 48 of the spool and the spring 50. The washer 60 provides amechanical stop to the spring compression. Additionally, the washer 60functions to define the neutral position of the spool 42. As shown inFIG. 1, the washer 60 contacts the bottom of the countersink region 34due to tension from spring 50 acting directly on the washer 60. Thewasher 60 also contacts the shoulder 48 of spool 42 due the tension fromspring 70 acting on the spool 42. The tension from spring 70 is somewhatless than the tension provided by spring 50 when the valve arrangement10 is in the neutral position. The washer 60 therein defines the neutralposition of the valve assembly 10 such that the starting position forthe proportional stroke of the solenoid assembly 28 is uniform inmanufacture, regardless of minor variations in the tension provided bysprings 70 and 50. Likewise, the washer 60 defines a neutral positiongap 64 between the work port and tank port, which will be discussed indetail below.

It is to be understood that spring compression may be adapted to variousapplications by modifying the length of the spring retaining member, thethickness of the washer, the stiffness of the spring, or other variousstructural features as would be obvious to one of ordinary skill in theart.

In the illustrated embodiment, the bore 24 is manufactured as a throughbore extending through the valve body 26. It is contemplated that thebore 24 may also be configured as a blind bore. A threaded cap or plug72 is positioned proximate the first end 36 within the bore 24 of thevalve assembly 10. The plug 72 functions as a stationary component inoperation with a dowel 40 and the relative movement of the spool 42.

The spool 42 is operatively arranged with the dowel 40 so as to sliderelative to the dowel 40. The presence of the dowel 40 causes a firstsurface area 100 of the spool, (shown in FIG. 4) to be less than anopposing surface area 102 of the spool 42 (shown in FIG. 5). Thesesurface areas 100 and 102 create an unbalanced pressure load on thespool 42 when the valve body is pressurized. This unbalanced pressureload biases the spool 42 in the de-energized direction 38′.

Typically, the valve assembly 10 includes a feedback component or returnspring 70. In the illustrated embodiment, the return spring 70 isretained by the plug 72 and biases the spool 42 in the de-energizeddirection 38′. The spring 70 acts to return the spool 42, relative tothe dowel 40, to the neutral position (shown in FIG. 1) when thesolenoid valve 28 is de-energized. The spring may comprise any standardspring commonly used and known by those having skill in the art or anyother feed-back device such as pneumatic struts, electromagnets, orelastomeric force feed-back devices. Alternatively, the return spring 70may be omitted in applications where the unbalanced work port pressurealone is used to return the spool to the neutral position. The remainderof this disclosure will discuss operation of this embodiment includingthe return spring 70. It is to be understood that an embodiment omittingthe return spring operates in similar fashion in accordance with theprinciples disclosed.

In use, when pressurized fluid is desired to operate the working unit16, the solenoid valve 28 is energized. The solenoid begins developingaxial force from the neutral position shown in FIG. 1. The solenoidvalve 28 shifts or moves the spool 42 in the energized direction 36′ tothe energized position shown in FIG. 2. In the energized position,pressurized fluid is permitted to flow from the pressure port 18 arounda flow portion 68 of the spool 42 having a decreased diameter and to thework port 20 for operation of the working unit 16. At the same time,fluid flow to the tank port 22 is obstructed by a close fit between thesecond annular surface 32 of the valve body 26 and the second annularportion 46 of the spool 42.

The pressurized fluid acts on the imbalanced surface areas 100 and 102of the spool 42. As the pressure increases, the pressure forceapproaches the solenoid force and the spool 42 begins to move in thede-energized direction 38′. Spool movement in the de-energized direction38′ increases fluid communication with the tank port 22 and decreasesfluid communication with the pressure port 18, thereby causing pressureat the work port 20 to stabilize or drop. With pressure drop, net forcein the energized direction 36′ exceeds net force in the de-energizeddirection 38′ causing movement in the energized direction 36′. Spoolmovement in the energized direction 36′ decreased fluid communicationwith the tank port 22 and increases fluid communication with thepressure port 18. This process or cycle causes “modulation” (i.e. backand forth movement) of spool 42. During modulation, the solenoid remainsenergized. The spool modulates until the pressure force and spring force70 is balanced against the solenoid force. At steady state equilibrium,(when the kinematic energy forces resulting from a changes in solenoidcurrent or brake pressure have subsided) the spool 42 will attain astabilized position where fluid flow from the pressure port to the workport equals the fluid flow from the work port to the tank port.

Upon desired release of the pressurized fluid, the solenoid valve 28 isde-energized and no longer produces solenoid force in the energizeddirection 36′. The spool 42 moves in the de-energized direction 38′ bythe imbalance of pressure force and the force from the return spring 70.At the neutral position there is still significant residual work portpressure, as the spool 42 has not traveled far enough to accommodatesufficient relieving fluid flow. The combination of the return springforce, and the force resulting from the residual work port pressurecompresses the opposing spring 50 to allow the spool 42 to move beyondthe neutral position to the relieving position (as shown in FIG. 3). Inthe relieving position, pressurized fluid is permitted to rapidly flowfrom the work port 20 around the flow portion 68 of the spool 42 and tothe tank port 22.

As the fluid is released, the fluid pressure force acting to compressspring 50 decreases. The spring 50 eventually overcomes the combinedforces and shifts the spool 42 forward to the neutral position shown inFIG. 1. In this position, the necessary fluid flow need only accommodateleakage from the pressure port 18 into the bore 24 to prevent unwantedpressure buildup from actuating the working unit 16. The washer 60contacting the bottom surface of the countersink area 34 determines theneutral position of the spool.

Referring back to the energized position of FIG. 2, fluid communicationis provided from the pressure port 18 through a pressure port gap 62between the first annular portion 44 of the spool 42 and the annularsurface 30 of the valve body 26. Likewise, as shown in FIG. 1, when thespool 42 is in the de-energized, neutral position, fluid communicationis provided to the tank port 22 through a neutral gap 64. Further,referring now to FIG. 3, the spool 42 is shown in a full exhaust orrelieving position wherein a relieving gap 66 provides for fluidcommunication from the work port 20 to the tank port 22. The relievinggap 66 has a cross-sectional area that is greater than the neutral gap64. The neutral gap 64 need only accommodate a minimal flow rate toprevent unwanted build up of pressure in a brake line of a working unit16, for example. The relieving gap 66 is greater than the neutral gap 64to accommodate a greater flow rate for rapid release of the working unit16.

The cross-sectional area of the fill relieving gap 66 may be severaltimes greater in cross-sectional area than the neutral gap 64. In theillustrated embodiment, the cross-sectional area of the relieving gap 66is about 1.5 to 3.5 times greater. It is contemplated that in largerapplications, the ratio between the relieving gap and the neutral gapcan be up to 20 times greater. Accordingly, the flow rate through therelieving gap 66 is likewise greater than the flow rate through theneutral gap 64.

The required flow rate from the work port 20 to the tank port 22 isdetermined by the amount of flow required in the application, forexample, the amount of flow necessary to disengage a hydraulic actuatoror hydraulic brake within an acceptable amount of time. For a givenspool configuration, the open area or gap providing for fluidcommunication between ports is a function of spool stroke or spooltravel. Greater flow rates require greater cross-sectional flow areas orgaps and therein require the spool to travel farther to increase thearea of the gap. Similarly, when the solenoid is first energized therequired flow rate from the pressure port 18 to the work port 20 isdetermined by the amount of flow required in the application, forexample, the amount of flow necessary to actuate a hydraulic brakewithin an acceptable amount of time.

In conventional designs, the required flow rate from work port to tankport defined and fixed the neutral position; and the stroke equaled thesum of the travel required to accommodate the needed flow rate from thepressure port, any small overlap required to minimize leakage, plus thetravel required to accommodate the needed flow rate to the tank port. Inother words, the neutral position in conventional designs istraditionally also the fully released position.

In accordance with the principles disclosed, the stroke of theillustrated embodiments need only include the travel necessary toaccommodate the pressure port flow rate, any small overlap required tominimize leakage, plus a minor opening sufficient to handle steady stateor equilibrium leakage from the work port to tank port. The proportionalstroke length of the valve assembly 10 is not limited or depleted byhaving to account for travel to accommodate the required flow rate tothe tank port. Therein, the valve assembly 10 provides increased flowrate capacity for a given spool size, or proportional solenoid strokelength, not attainable by traditional arrangements. In the alternative,the valve assembly 10 may incorporate a smaller solenoid assembly tominimize cost or size of the valve assembly for a particular given flowrate capacity.

To further explain, when the solenoid 28 is switched from an energizedstate to a de-energized state, the pressurized fluid from the work port20 works in combination with the return spring 70 to bias the spool 42in the de-energized direction 38′. Upon solenoid de-energization, theimmediate work port fluid pressure is greatest. The combined pressureforce and return spring 70 force move the spool 42 to the relievingposition shown in FIG. 3, and at the same time compress the spring 50 inthe de-energizing direction 38′. The relieving gap 66, which exhauststhe pressurized fluid, is maximized to provide quick release orengagement of the working unit.

When the work port pressure begins to equalize with the tank portpressure, the spring 50 returns the spool to the neutral position in theenergized direction 36′, without assistance from the solenoid. In otherwords, the spool 42 travels from a first de-energized position to asecond de-energized position. This configuration and arrangement inessence shifts the neutral position of the valve assembly 10 forwardfrom the first de-energized position to the second de-energizedposition. By shifting the neutral position forward, maximum strokelength and thrust force are available to shift the spool 42 to anenergized position having greater flow capacity.

In typical prior art configurations, a fixed stroke length determinedthe valve's flow rate capabilities, i.e., a user requiring quickerexhausting capability would have to sacrifice input capability. In thepresent invention, the exhausting capability is maximized withoutsacrificing input capability by action of the spring 50 shifting theneutral position forward. In other words, the arrangement providesgreater actual stroke length without jeopardizing proportional traveland maximum thrust force.

FIG. 6 depicts, in cross-section, a second embodiment of a valveassembly 110 according to the principles of this disclosure. In general,the valve assembly 110 includes a valve body 126 coupled to a solenoidassembly 128. The valve body 126 of the valve assembly 110 includes abore 124, a pressure port 118, a work port 120, and a tank port 122. Inthis port configuration, the tank port 122 extends from the bore 124;however, the overall principles of operation of this secondconfiguration are similar to those disclosed in the first embodiment.

When the spool 142 is in the de-energized neutral position (shown inFIG. 6), fluid communication is provided from the work port 120 to thetank port 122 through a neutral gap 164. A cross-shaped washer orcomponent 174 accommodates fluid communication to the tank port 122 inthis embodiment. As best shown in FIGS. 9 and 10, the cross-shapedcomponent 174 includes recessed portions 176 through which fluid flows.The cross-shaped component 174 functions to provide a stationary centersurface 178 against which the dowel 140 may act. This permits unbalancedpressure forces to bias the spool 142 in the de-energized direction 182′relative to the dowel 140, as discussed previously.

In accordance with the principles disclosed, FIG. 7 illustrates thevalve assembly 110 in an energized position. Fluid communication isprovided from the pressure port 118 through a pressure port gap 162 andaround a flow portion 168 of the spool 142, to the work port 120.

Upon desired release of the pressurized fluid, the solenoid valve 128 isde-energized. Return spring 170 and the imbalance of pressure forcesmove the spool 142 to a relieving position shown in FIG. 8. Thecombination of the return spring force, and the force resulting from theresidual work port pressure compresses opposing spring 150 to allow thespool 142 to move beyond the neutral position to the relieving position.(As discussed previously, the return spring 170 may be omitted.) In therelieving position, the relieving gap 166 provides a greatercross-sectional area than the neutral gap 164 for rapid fluid flow fromthe work port 120 to the tank port 122. As fluid is exhausted, the fluidpressure force acting to compress spring 150 decreases. The spring 150eventually overcomes the combined forces and shifts the spool 142 in theenergized direction 180′ to the neutral position (shown in FIG. 6),without having to energize the solenoid 128. Overall, this secondembodiment provides all the advantages in accordance with the principlesdisclosed by the first embodiment. Additionally, the second embodimentis beneficial by reducing manufacturing operations. Specifically, oneport, i.e. the tank port 122, is configured as an extension of the valvebody bore 124 and therein eliminates machining a separate tank port.

The above specification and examples provide a complete description ofthe manufacture and use of the composition of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the principles disclosed, the invention resides inthe claims hereinafter appended.

I claim:
 1. A method of controlling fluid flow in a valve arrangement,the valve arrangement including a valve body having a pressure port, awork port, and a tank port, a solenoid device coupled to the valve body,and a spool operably coupled to the solenoid device, the methodcomprising: (a) pressurizing the work port by energizing the solenoiddevice and moving the spool a first distance from a neutral position toa pressurized position; (b) relieving the work port by de-energizing thesolenoid device and moving the spool a second distance to a relievingposition, the second distance being greater than the first distance, thevalve arrangement being configured to provide a first gap for fluidcommunication between the work port and the tank port when the spool isin the relieving position, the first gap of the valve arrangement havinga first cross-sectional area; and (c) moving the spool, withoutenergizing the solenoid device, from the relieving position to theneutral position, the valve arrangement being configured to provide asecond gap for fluid communication between the work port and the tankport when the spool is in the neutral position, the second gap of thevalve arrangement having a second cross-sectional area, the firstcross-sectional area of the first gap being greater than the secondcross-sectional area of the second gap.
 2. The method of claim 1,wherein the first cross-sectional area of the first gap is up to 20times greater than the second cross-sectional area of the second gap. 3.The method of claim 1, wherein the first cross-sectional area of thefirst gap is about 1.5 to 3.5 times greater than the secondcross-sectional area of the second gap.
 4. The method of claim 1,wherein the second cross-sectional area of the second gap is sized andconfigured to accommodate leakage from the pressure port into the valvearrangement to prevent unwanted pressure buildup within the work port.5. The method of claim 1, wherein the valve arrangement includes onlyone solenoid valve.